/**********************************************************************
 * SailmiPIM - modular cross-platform feature Personal Information Manager Tools.
 * Copyright(C) 2006-2014  Georg Rudoy
 *
 * Distributed under the Boost Software License, Version 1.0.
 *(See accompanying file LICENSE or copy at https://www.boost.org/LICENSE_1_0.txt)
 **********************************************************************/

#pragma once

#include "utilconfig.h"
#include <QByteArray>
#include <QSet>
#include <QDataStream>
#include <QtDebug>

namespace SailmiPIM::Util
{
	/** @brief A simple pool of identificators of the given type.
	 *
	 * This class holds a pool of identificators of the given type \em T.
	 * It is very simple and produces consecutive IDs, this \em T should
	 * support <code>operator++()</code>.
	 */
	template<typename T>
	class IDPool final
	{
		T CurrentID_;
	public:
		/** @brief Creates a pool with the given initial value.
		 *
		 * @param[in] id The initial value of the pool.
		 */
		explicit IDPool(const T& id = T())
		: CurrentID_ { id }
		{
		}

		/** @brief Returns next ID.
		 *
		 * @return Next ID in the pool.
		 */
		T GetID()
		{
			return ++CurrentID_;
		}

		/** @brief Forcefully sets the current ID.
		 *
		 * @param[in] id The new current ID.
		 */
		void SetID(T id)
		{
			CurrentID_ = id;
		}

		/** @brief Frees the id.
		 *
		 * @param[in] id The ID to free.
		 */
		void FreeID(T id)
		{
			Q_UNUSED(id)
		}

		/** @brief Saves the state of this pool.
		 *
		 * @return The serialized state of this pool.
		 */
		QByteArray SaveState() const
		{
			QByteArray result;
			{
				QDataStream ostr(&result, QIODevice::WriteOnly);
				quint8 ver = 1;
				ostr << ver;
				ostr << CurrentID_;
			}
			return result;
		}

		/** @brief Recovers the state of this pool.
		 *
		 * @param[in] state The state of this pool obtained from
		 * SaveState().
		 */
		void LoadState(const QByteArray& state)
		{
			if(state.isEmpty())
				return;

			QDataStream istr(state);
			quint8 ver;
			istr >> ver;
			if(ver == 1)
				istr >> CurrentID_;
			else
				qWarning() << Q_FUNC_INFO
						<< "unknown version"
						<< ver
						<< ", not restoring state.";
		}
	};
}
